Programmable PHY for broadband wireless access systems

ABSTRACT

A system and method for communication between a wireless modem and wireless hub on a selected downstream channel of a plurality of downstream channels is provided. The selected downstream channel is selected by the wireless modem after receiving communication parameters for each of the downstream channels and selecting the selected downstream channel by determining the most efficient of the downstream channels at that time for downstream communication.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This invention claims priority to the following co-pending U.S.provisional patent applications, each of which are incorporated hereinby reference, in their entirety:

[0002] Shahar, Provisional Application Ser. No. 60/178,156, entitled“Programmable PHY For Broadband Wireless Access,” attorney docket no.23600.00900, filed, Jan. 26, 2000;

[0003] Jonas et al, provisional Patent Ser. No. 60/178,138, entitled“Two Dimensional Scheduling Scheme For Broadband Wireless AccessSystem,” attorney docket no. 23600.0800, filed, Jan. 26, 2000; and

[0004] Asia et al, provisional Patent Ser. No. 60/178,303, entitled “AUnidirectional Communication Scheme For Remote Maintenance And Controlin A Broadband Wireless Access System,” attorney docket no. 23600.01200,filed, Jan. 26, 2000.

BACKGROUND OF THE INVENTION

[0005] 1. Field of Invention

[0006] The present invention relates to broadband wireless accesssystems and, among other things, to a programmable PHY for use inbroadband wireless access systems.

[0007] 2. Discussion of Background

[0008] Point to multi-point fixed broadband wireless access systems overMMDS networks are known in broadcast situations. These networks operateover licensed bands including the MMDS band (2,150 to 2,162 MHz), theWCS band (2,305 to 2,311 MHz) and the ITFS/MMDS bands (2,500 to 2,686MHz).

[0009] A known wireless broadband access system, which operates at arange of between 50 MHz and 864 MHz, but not in the MMDS, WCS, orITFS/MMDS bands, is the data over cable specification system, which isspecified in the data over cable system interface specifications(DOCSIS). An overview of a wireless DOCSIS system is depicted in FIG. 1.A CMTS 10 communicates with a wide area network 20, such as theInternet. The CMTS 10 can transmit signals from the wide area network 20along a cable network 30 through cable modems 40 to CPE 50. CPE 50messages can be transmitted to the wide area network 20 through thecable modem 40 along the cable network 30 to the CMTS 10.

[0010] In point to multi-point broadband wireless access systems onecentral end-point, e.g. the head-end, communicates through abi-directional link or links with multiple end-points, e.g. the nodes.The number of nodes in communication varies in time and can be none, oneor two or more at any specific time.

[0011] The link(s) between the head-end and the nodes are combined inone or more channels. The signal path from the central end-point to thenodes is referred to as downstream, while the signal path from the nodesto the central end-point is referred to as upstream.

[0012] A single upstream channel can be used to deliver information froma node to the head-end and downstream channels are used from thehead-end to a node or a group of nodes. If a single upstream channel isused for communication from the nodes(s) to the central point, then onlyone end-point can sends information on the single upstream channel atany one time.

[0013] Additionally, in such a system the diverse topological conditionsof each user within the service area in terms of factors such as signalto noise, multi-path and fading makes it difficult to implement aflexible communication scheme that will enable per user optimizationwith respect to robustness and throughput.

SUMMARY OF THE INVENTION

[0014] In one embodiment, the present invention provides for a systemand method for communication between a wireless modem and wireless hubon a selected downstream channel of a plurality of downstream channels.The selected downstream channel is selected by the wireless modem afterreceiving communication parameters for each of the downstream channelsand selecting the selected downstream channel by determining the mostefficient of the downstream channels at that time for downstreamcommunication.

[0015] In another embodiment, the present invention provides for asystem and method for communication between a wireless modem andwireless hub on a selected one downstream channel of a plurality ofdownstream channels. The selected upstream channel is selected by thewireless modem after receiving communication parameters for each of theupstream channels and selecting the selected upstream channel bydetermining the most efficient of the upstream channels at that time forupstream communication. It is also possible that this embodiment, iscombined with the first embodiment such that the plurality of upstreamchannels are associated with the selected downstream channel.

[0016] The present invention may be embodied as a method for selecting achannel for communication between two wireless devices, comprising thesteps of synchronizing a wireless modem with a wireless hub on adownstream channel of a plurality of downstream channels bysynchronizing the symbol timing, forward error correction framing, andrecognition of a synchronization message at the wireless modem, thechannel of the plurality of downstream channels being transmitted fromthe wireless hub to a plurality of wireless modems including thewireless modem, receiving at the wireless modem on the downstreamchannel a message comprising information regarding the parameters forcommunicating over each of the plurality of downstream channels,determining a selected downstream channel of the plurality of downstreamchannels for communication with the wireless hub, and re-synchronizingthe wireless modem with the wireless hub on the selected downstreamchannel of the plurality of downstream channels.

[0017] The present invention may also me embodied as a wirelesscommunication system, comprising, a wireless hub configured to senddownstream communications on at least one of a set of predefineddownstream channels and receive upstream communications on at least oneof a set of predefined upstream channels, at least one wireless modemconfigured to receive said downstream communications, and send saidupstream communications, wherein said wireless modem comprises, anacquisition unit configured to acquire a predefined downstream channeltransmitted by said hub and read DCD messages describing availabledownstream channels, a scanning unit configured to scan the availabledownstream channels, and a selection unit configured to select the bestavailable downstream channel.

[0018] The present invention also includes A communication device,comprising, a hub configured to send downstream communications on atleast one of a set of predefined downstream channels and receiveupstream communications on at least one of a set of predefined upstreamchannels, wherein: said hub includes a DCD message generator thatconstructs at least one DCD message sent on said downstream channels,and said at least one DCD message defines all downstream channelsutilized by said hub; and a modem unit for use in a communicationsystem, comprising, a reception unit configured to receive downstreamcommunications on a current downstream channel, and a downstream channelselection unit to read DCD messages received by said reception unit andselect a best available channel as said current downstream channel frompriorities contained in said DCD messages.

[0019] Each of the method, system, device, and modem may be convenientlyimplemented on a general purpose computer, or networked computers, andthe results may be displayed on an output device connected to any of thegeneral purpose, networked computers, or transmitted to a remote devicefor output or display.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0021]FIG. 1 is an overview of a known data over cable system;

[0022]FIG. 2 is a block diagram of a wireless hub communicating with awireless modem in a broadband wireless access system according to apresently preferred embodiment of the present invention;

[0023]FIG. 3 is a flow chart illustrating acquisition of a downstreamchannel according to an embodiment of the present invention;

[0024]FIG. 4 is a flow chart illustrating changing of a downstreamchannel according to an embodiment of the present invention; and

[0025]FIG. 5 is a flow chart illustrating acquisition of an upstreamchannel according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring again to the drawings, wherein like reference numeralsdesignate identical or corresponding parts, and more particularly toFIG. 2 thereof, there is illustrated, in the presently preferredembodiment, a single carrier modulation scheme is selected for bothdownstream communication 110 and upstream communication 120, between awireless hub 130 and a wireless modem 140. The wireless modem 140 can beone of a plurality of wireless modems in communication with the wirelesshub 130. The selection of a single carrier modulation scheme allows forthe flexibility of multiple single carrier constellations, multiplechannel bandwidth, multiple roll off factors, multiple symbol rates,multiple FEC schemes and multiple preambles (upstream only). Further,the wireless modem can be considered a customer premises indoor unit(CPE IDU) that communicates with a customer premises outdoor unit (CPEODU), that includes the transmission and reception equipment for thecustomer device. The wireless hub also utilizes one or more outdoor andindoor units, each set of which can be referred to as a Wireless ModemTermination System (WMTS) or Base Station (BS).

[0027] The presently preferred parameters for the downstream channel aredescribed in Table 1 below. TABLE 1 Constellation Symbol rate Channel BWRoll off FEC 64QAM 5.056941 Msps 6 MHz .18 ITU-T J.83 Annex B 64QAM6.942 Msps 8 MHz .15 ITU-T J.83 Annex A 16QAM QPSK 64QAM 5.304 Msps 6MHz .13 ITU-T J.83 Annex A/C 16QAM QPSK 64QAM 3.536 Msps 4 Mz .12-.15ITU-T J.83 Annex A/C 16QAM QPSK 64QAM 1.768 Msps 2 MHz .12-.15 ITU-TJ.83 Annex A/C 16QAM QPSK 64QAM 1.326 Msps 1.5 MHz .12-.15 ITU-T J.83Annex A/C 16QAM QPSK VSB DVB-T QPSK DVB-S ⅞, ⅚, ¾, ⅔, ½

[0028] In operation, it is preferred that a downstream demodulator inthe wireless modems employ an equalizer with which can compensate adelay spread of more than 10 μs @ 5 Msps. The 10 μs figure is calculatedas a maximum delay spread due to a number of factors such as multi-path.Although 10 μs is preferred, the delay spread may typically range from 0to 20 μs

[0029] The presently preferred parameters for the upstream channel aredescribed in the table 2 below: TABLE 2 Constellation Symbol RateChannel Width QPSK, 16QAM 160 ksps 200 kHz QPSK, 16QAM 320 ksps 400 kHzQPSK, 16QAM 640 ksps 800 kHz QPSK, 16QAM 1,280 ksps   1,600 kHz   QPSK,16QAM 2,560 ksps   3,200 kHz  

[0030] Although Table 1 and 2 specify QAM and QPSK constellations, otherconstellations such as BPSK and other modulation types may be utilizedin conjunction with the present invention without departing from itsscope.

[0031] The presently preferred FEC employed in upstream transmission isa programmable Reed Solomon code as described in DOCSIS RFI documentSP-RFIv1.1-I03-991105 chapters 4 & 5. DOCSIS RFI documentSP-RFIv1.1-I03-991105, and the other DOCSIS specifications areincorporated herein by reference in their entirety as if fully set forthherein. While the presently preferred preamble is programmable as perDOCSIS RFI document SP-RFIv1.1-I06-001215 chapters 4 & 5, a longpreamble is used for per-burst post equalization by the burst receiver.

[0032] The diverse propagation conditions of the users within theserving area call for the independent selection of an upstream and adownstream channel pair for each wireless modem, user, from a group ofavailable channels. The selection of the channel pair is performedduring initialization and is then preferably updated on a continuousbasis.

[0033] The initialization procedure in general is based on the DOCSISinitialization procedure as described in RFI SpecificationsSP-RFIv1.1-I06-001215, chapter 9.2.

[0034] The following are additional functions that are preferred to beperformed in addition to the RFI DOCSIS specification to facilitate thewireless channel selection:

[0035] A MAC domain is defined as a group of several downstream channelsand several upstream channels. This will typically be the group ofchannels that can be used by the user population, the wireless modems,in communication with the particular wireless hub, within a serving area(e.g., a sector of an MMDS cell).

[0036] A sector refers to one location that serves an area, each channelserves only a certain geographic sector, using a directional antenna.For example, one antenna for a quadrant between north and east, a secondantenna for the quadrant from east to south, a third antenna for thequadrant between south and west, and a fourth antenna for the quadrantbetween west and north (however, many different variations of sectorsize, including sectors of unequal area may also be utilized). Thesectors may be numbered for identification (1=N&E, 2=E&S, 3=S&W, and4=W&N, for example).

[0037] The several downstream and upstream channels of the MAC domainare typically:

[0038] 1. Controlled by the same entity;

[0039] 2. Modems and service Ids are unique; and

[0040] 3. A modem uses downstream and upstream channels in the same MACdomain.

[0041] Any new MAC messages defined below, which are not defined in anyof the DOCSIS current standards, and MAC messages that have been changedand are DOCSIS non-complaint are presently preferred to be indicated bya new type number. For example, for the current version 1.1, of DOCSIS,all new or non-complaint MAC messages would have a type number of 129and larger.

[0042] All downstream channels within the MAC domain will havetransmitted on them a Bandwidth Allocation messages with respect to allthe upstream channels within the group. These Bandwidth Allocationmessages can be standard DOCSIS MAP messages or the MAP2D messagedescribed in Provisional Patent Application, Ser. No. 60/178,138, titled“Two-Dimensional Scheduling Scheme For A Broadband Wireless AccessSystem,” by the same inventors of this application.

[0043] All downstream channels within the MAC domain will furtherinclude a Downstream Channel Descriptor (DCD) messages. These DCDmessages will be transmitted periodically to the wireless modems by thewireless hub. Once a wireless modem acquires a downstream channel (oneof the downstream channels available within the MAC domain), thewireless modem will capture the DCD message with respect to all thedownstream channels that belong to the MAC domain. The DCD message willcontain the following information for each downstream channel: (1) IFfrequency; (2) RF frequency; (3) Modulation type; (4) Symbol rate; (5)bandwidth; (6) roll off factor; (7) FEC Scheme; (8) Criteria forswitching to another downstream channel; (9) priority information toselect a downstream channel for communication for a newly initializingmodem; and (10) priority information when switching to a new downstreamchannel for a modem already in communication with wireless hub.

[0044] A single DCD message describes channels that service the samesector. If a downstream channel can service more than one sector, it isincluded in all the respective DCD messages. The information on all thedownstream channels for a sector is included in a single DCD messages ormay be delivered in a separate DCD messages. An advantage to separateDCD messages is that smaller messages are more robust.

[0045] The WMTS generates DCD messages in the format shown in Table 3,including all of the following parameters: TABLE 3 Downstream ChannelDescriptor (DCD)

[0046] There may be more than one channel descriptor in one DCD message.Each channel description (see table 6) defines one channel. There is nodifference between the formats of preceeding and subsequent channeldescriptions. TABLE 4 Downstream Channel Descriptor Descriptions MACManagement As defined in DOCSIS Type = 129. Message Header Sector IDIdentifier of the geographic sector, which can use these downstreamchannels (1-255). If sector information is not used, a single valueshould be indicated in all DCD messages. Cell ID Identifier of the Cellwhere this message is trans- mitted (1-255). If cell information is notbeing used, a single value should be indicated in all DCD messages.Configuration Incremented by one (modulo the field size) by the ChangeCount (8 WMTS-IDU, whenever any of the values of any of bits) thedownstream channel descriptors change.

[0047] All other parameters are presently preferred to be coded as TimeLength Value (TLV) fields, as defined in DOCSIS RFI specification6.2.1.3.2. The advantage of TLV fields for application of the presentinvention is the flexibility to allow different field combinations inthe message being transmitted and the ability to upgrade by addingadditional types while maintaining backward compatability. The typevalues used are defined in table 5, for sector parameters, and table 6,for downstream channel attributes. Sector-wide parameters (types 1-2 inTable 3) are presently preferred to be required to precede channeldescriptors (type 3 below).

[0048] TLV (Time Length Value) parameters for the overall MAC domaindownstream are described in Table 5 below: TABLE 5 Sector TLV ParametersType (1 Length Value Name byte) (1 byte) (Variable length) Control 1 1Downstream ID for the channel to be channel used as control channel.Number of 2 1 Number of downstream channels channels that are availablefor this sector. This number may include channels that are defined inother DCD messages. Channel 3 Variable May appear more than once.Descriptor Described below. The length is the number of bytes in theoverall object. including embedded TLV items.

[0049] Channel descriptors are compound encoded TLVs that define theparameters, for each downstream channel. Within table 6 each channeldescriptor is an unordered list of attributes, encoded as TLV values:TABLE 6 Channel TLV Parameters Len- Type gth (1 (1 Value Name byte)byte) (Variable length) Downstream  1 1 The Identifier of the downstreamChannel ID channel to which this message refers. RF Frequency  2 4 RFfrequency in KHz IF Frequency  3 4 IF frequency in KHz Modulation type 4 1 0 = Adaptive, 1 = QPSK, 2 = 16QAM, 3 = QAM64, 4 = QAM256 Symbolrate  5 4 Symbol rate (bps) Bandwidth  6 4 Bandwidth (Hz) Roll offFactor  7 1 200 * Roll of factor FEC scheme  8 1 1 = ITU-T J.83 AnnexA/C 2 = ITU-T J.83 Annex B 3 = Adaptive FER Threshold  9 4 Threshold offailed MPEG Frames. If the number of failed frames is more than thisnumber, a downstream channel switching MUST be initiated as defined in0. The counting of failed frames is initialized after each measurementperiod as defined in the FER measurement period TLV parameter. Priorityfor a new 10 1 Priority to be used by a new modem- CPE IDU Lowest numberis higher priority. Priority for 11 1 Priority to be used if the currentchanging channel channel has poor conditions-Lowest number is higherpriority. Cell ID 12 1 The Identifier of the Cell which transmit thedescribed downstream channel FER 13 1 Time period for MPEG Frame Errormeasurement Rate measurement (See FER period Threshold TLV parameter).Time is given in seconds, in the range of 1- 255 Sec.

[0050] The priority value is determined by the BS IDU. The priority ispresently preferred to be dynamically changed by the WMTS-IDU betweenDCD messages. Such changes may be used to balance the load between thechannels. A different priority can be assigned for a new initializingmodem or to a registered modem that has to switch channel due to poor RFconditions. The later priority may depend on the current channel, insuch a way that different priorities will be assigned in DCD messagesthat are delivered on different channels.

[0051] The method to assign priority values to each channel is operatordependent. A presently preferred priority assignment method is to simplycalculate the ratio of channel bandwidth to per user on each channel,where the number users used in the calculation is one plus the number ofactual users. The highest priority is then preferably assigned to thosechannels that have the highest ratio, i.e. those with the largestbandwidth per user are assigned the highest priority. Another method toassign priorities would be to use fixed priorities, such as: Higherpriority for a higher order modulation scheme; For the same modulation,higher priority for a higher symbol rate; For the same modulation andsymbol rate, higher priority for a stronger FEC scheme.

[0052] Although other priorities schemes may be utilized, it ispreferred that the priorities are assigned a numerical designation ofpriority. For example, when a modem initializes, it will try to usepriority 1 channels. If this fails, the modem will attempt to initializeon priority 2 channels and so on. If a modem is already on a channel butthere are too many errors, the modem will try to work on other channelsin the same way, but based on the priorities for changing channels.

[0053] The MAC domain id, which herein is equivalent to the sector id ofthe modem, may be required in if the upstream sectorization is differentfrom the downstream sectorization (e.g. omni downstream channel withsectorized upstream). The MAC domain id can be used in this case by thewireless modem to determine whether the respective downstream channel isapplicable to its transmission capability. This determination is donea-priori with information that is conveyed to the modem from a localterminal or remotely using a downstream control channel.

[0054] The modem will try to resynchronize to the “best” downstreamchannel by starting from channel the highest priority level field andcontinuing down the priority levels until it achieves synchronization.

[0055] Optionally, initial downstream channel acquisition will befacilitated by configuring one or more of the downstream channels withQPSK, BPSK or other modulation and letting the wireless modems searchinitially for this type of channel. This type of channel may be used asa control channel, therefore allowing for multiple control channelsAfter this channel is established and a DCD message is received on thischannel, the wireless modem can select the “best” downstream channelaccording to the above-described procedure.

[0056] Faster downstream acquisition can also be facilitated bypreferably scanning only MMDS center frequencies.

[0057] All downstream channels within the MAC domain, which is alsopreferred to be the sector of the modem, will carry Upstream ChannelDescriptors (UCD) messages with respect to all the upstream channelswithin the MAC domain. UCD messages with respect to upstream channelsthat do not belong to the MAC domain will not be transmitted on thedownstream channels that belong to the MAC domain. Alternatively, in thecase of a downstream channel that is used within more than a single MACdomain, each UCD message will have a MAC domain id field. This field aswell as a priority field will be added to the standard DOCSIS UCDmessage structure. The priority field will be used by the wireless hubto allow prioritization of channels on a dynamic basis, consideringcriteria such as load balancing.

[0058] The presently preferred Upstream Channel Descriptor (UCD) messageis altered from the UCD message specified in the DOCSIS specification bychanging the TLV as described in table 7 below: TABLE 7 Additional TLVparameters for Modified UCD message Type (1 Length Value Name byte) (1byte) (Variable length) Sector 129 1 Identifier of the geographic sectorwhich can use these downstream channels. This parameter may appear morethan once, if the same upstream channel may be used by more than onesector. Number of 130 1 Number of upstream channels that channels areavailable for this sector Criteria for 131 Operator Channel attenuation,occurrence of switching Defined unacknowledged transmissions, etc.channels Priority for a 132 1 Priority to be used by a new modem- newCPE IDU Lowest number is higher priority. Priority for 133 1 Priority tobe used if the current changing channel has poor conditions-Lowestchannel number is higher priority. Cell ID 136 1 Identifier of the Cellwhere this message is transmitted. The described upstream channel shouldbe used on this cell.

[0059] The priority value is calculated dynamically by the wireless hubIDU. For each channel, the available bit rate (without PHY overhead)should be divided by the estimated number of active users on thischannel, plus one. The channel with the highest result will get priority1, the next 2, etc. In this scenario, the same priority will be used forboth new modem initialization or for changing upstream channels forwireless modems already in communication with the WMTS.

[0060] Once a modem acquires a downstream channel, the modem willcapture UCD messages with respect to all the upstream channels thatbelong to the sector. The modem will then select the “best” channel torange according the highest priority channel on which it is capable ofcompleting a ranging transaction.

[0061] The above procedure will be repeated until the modem hassuccessfully ranged and established IP connectivity with the wirelesshub.

[0062] It is also possible for the modem to continuously monitor the DCDmessages, which are periodically transmitted, and switch to another,more robust channel if the performance on the current channel is notacceptable. The downstream channel switching protocol and parameters aredetermined in the same way as described above with respect to selectionof a downstream channel at initialization. However, the downstreamchannel changing protocols can also be different than that atinitialization, since the wireless hub already has information regardingthe communication capabilities for one or more channels of modem withwhich it is in communication.

[0063] When the wireless hub determines that the wireless modem shouldswitch to another downstream channel it transmits a downstream channelchange request (DCC-REQ). The format of a DCC-REQ message is shown intable 8 below: TABLE 8 Downstream Channel Change Request

[0064] The parameters of the DCC-REQ message of table 8 is defined intable 9 below: TBALE 9 Downstream The identifier of the downstreamchannel to which the Channel ID CPE IDU is to tune for downstreamtransmissions. This is an 8-bit field.

[0065] A Downstream Channel Change Response (DCC-RSP) is transmitted bythe CPE IDU in response to a received Downstream Channel Change Requestmessage to indicate that it has received the DCC-REQ and it is tuned tothe new downstream channel. The DCC-RSP can be also be transmitted bythe CPE IDU without a preceding DCC-REQ, if the CPE IDU switches adownstream channel, due to high signal to noise ratios, low receivedpower, high error rates, or other reception problems. The format of aDCC-RSP message is shown in table 10 below. TABLE 10 Downstream ChannelChange Response

[0066] Parameters of Table 10 are described in Table 11 below: TABLE 11Downstream The identifier of the downstream channel to which the CPEChannel ID IDU is tuned for downstream transmissions. This is an 8-bitfield.

[0067] The CPE IDU ignores a DCC-REQ message, by not responding with aDCC-RSP message, if it receives the DCC-REQ while it is in the processof performing a channel change. When a CPE IDU receives a DCC-REQmessage requesting that it switch to a downstream channel that it isalready using, the CPE IDU responds with a DCC-RSP message on thatdownstream channel indicating that it is already using the correctchannel.

[0068] A Downstream Channel Change Acknowledgement (DCC-ACK) istransmitted by a BS IDU in response to a received Downstream ChannelChange Response message to indicate that it has received the DCC-RSP.The format of a DCC-ACK message is shown in Table 12. TABLE 12Downstream Channel Change Acknowledgement

[0069] Parameters of the DCC-ACK are shown below in table 13: TABLE 13DownstreamChannel The identifier of the downstream channel to ID whichthe CPE IDU is tuned for downstream transmissions. This is an 8-bitfield.

[0070] When the BS IDU receives a DCC-RSP message, regarding the currentdownstream channel of the CPE IDU, according to the BS IDU tables, theBS IDU MUST respond with a DCC-ACK message on that channel indicatingthat it is already using the correct channel.

[0071] The full procedure for changing channels is described in Section6 of the DOCSIS RFI Specification version 1.1.

[0072] An Upstream Channel Change Response is transmitted by a BS IDU inresponse to a received Upstream Channel Change Response message toindicate that it has received the UCC-RSP. When a BS IDU receives aUCC-RSP message, regards the current upstream channel group of the CPEIDU, according to the BS IDU tables, the BS IDU MUST respond with aUCC-ACK message, indicating that it is already using the correct channelgroup. TABLE 14 Upstream Channel Change Acknowledgement Bit 0 8 16 24 31Mac Management Message Header Upstream group ID

[0073] Parameters of Table 14 are as follows: TABLE 15 Downstream Theidentifier of the downstream channel to which Channel ID the CPE IDU istuned for downstream transmissions. This is an 8-bit field.

[0074] Acquisition of a Downstream Channel

[0075] BS IDU Requirements

[0076] The BS IDU should periodically transmit a Downstream ChannelDescriptor (DCD) message. This message defines the available downstreamchannels. The BS IDU may be configured to send a single DCD message (oneach channel), which describes all the available channels. Anotheroption is to send a separate message for each downstream channel. Thesecond alternative enables more reliable reception, due to a shortermessage length, on a poor channel. The DCD messages, for all thedownstream channels that serve one downstream sector, should betransmitted on each of these downstream channels.

[0077] CPE IDU Requirements

[0078] Initial Connection

[0079] 1. A CPE should first try to lock on any downstream channel toget an updated DCD message (See FIG. 3, step 300). The CPE evaluateschannels according to the following order:

[0080] a. A control channel that may be optionally pre-configuredlocally or remotely to the CPE-IDU. A list of standard control channelsmay be optionally pre-configured into the wireless modem. In addition,the control channel identification may be changed during operation byone or more of the following methods: (i) locally, by a technician, (ii)remotely, by using the SNMP to transmit instructions during downstreamcommunication, (iii) remotely, using a unidirectional service mode, suchas described in U.S. Provisional Patent Application Ser. No. 60/178,303,now U.S. patent application Ser. No.______ which is incorporated hereinby reference, in its entirety, as an example; and (iv) remotely, in aDCD message transmitted during a previous operating session of thewireless modem. If the wireless modem cannot lock on a control channelor the specific implementation does not make use of control channels orthe wireless modem has not configured with the control channels list,the CPE-IDU will skip this step.

[0081] b. The last channel where the CPE has been connected in aprevious session.

[0082] c. The other channels which have been defined by DCD message inprevious session.

[0083] d. Scanning the entire available spectrum and automaticallyacquire the modulation and channel width.

[0084] 2. After successful acquisition of the first downstream channel,as defined in DOCSIS, the CPE waits for a DCD message (step 310). If anon-zero sector ID is configured for the CPE, only DCD messages withthis sector ID should be processed. If necessary, as indicated by the“Number of Channels” parameter in the DCD message, it continues toreceive DCD messages until it has the parameters for all the channels.

[0085] The sector parameters of a wireless modem are preferablyconfigured by one of the following methods: (i) locally, by atechnician, (ii) remotely, by using the SNMP to transmit instructionsduring downstream communication, (iii) remotely, using a unidirectionalservice mode, and (iv) remotely, utilizing Sector Configuration List(SCL) messages which contain MAC addresses for the sectors in which themodem is capable of communicating.

[0086] If a CPE IDU is assigned manually or automatically a Sector ID ofzero, it may use all the upstream and downstream channels, regardless oftheir defined sector.

[0087] 3. If after a configured time out, (10 Seconds is a typicalvalue), which starts when the CPE is synchronized to the downstreamchannel, as defined in 9.2.1 of the DOCSIS specifications, the CPE hasnot received all the DCD messages, it tries to lock on the channelsdefined by the received DCD messages (with sector limitation, ifdefined), following the priority order (step 320). These channels shouldthen be used to receive the DCD messages for the remaining channels forwhich a DCD message was not received (step 340).

[0088] 4. After receiving the parameters of all the available downstreamchannels for its sector, a CPE will try to lock on the downstreamchannels, according to the assigned priorities for a new CPE (step 350).The channel to be selected is the acceptable one with highest priority.The acceptable channel with highest C/N ratio is selected from channelswith the same priority. Acceptable channel is a channel where the CPEcan successfully complete the registration process. The followingprocess achieves this selection:

[0089] The CPE MAY skip channels that it has failed to lock on duringthe previous steps. A CPE should start with the highest prioritychannels and proceed to lower priorities, until it successfully connectsto a channel (receiving SYNC messages, as defined by DOCSIS). Aftersuccessfully connecting to a channel, the CPE should continue to checkall the channels with the same priority. The channel with highest C/Nratio from these channels, with the same priority, is selected and usedto continue with upstream acquisition. If upstream acquisition, usingthis channel fails, the next downstream channel is used.

[0090] 5. The CPE should establish a channel quality table (step 360).The table should include the following parameters for each channel:

[0091] a. Acquisition result—Success, one failure or two failures.Should be stored for each tested channel. Other channels should bemarked as unknown.

[0092] b. Carrier to Noise ratio—Should be stored for each acquiredchannel.

[0093] c. MPEG frames error rate—The measurement period should be asdefined in the DCD FER measurement period TLV parameter. The measurementcan be terminated earlier if the error rate threshold is exceeded.

[0094] d. A channel status should be changed to unknown after T9interval without being tuned to that channel.

[0095] Changing of a Downstream Channel

[0096] If the frame error rate on the current downstream channel is notacceptable, according to the “FER Threshold” TLV parameter in the DCDmessage, the CPE should switch a downstream channel (See FIG. 4, step400). It should use the information from the last successfully receivedDCD messages (step 410). The CPE should try to lock on the downstreamchannels, according to the assigned priorities for changing channel(steps 420/430). Channels that have been tried in the previousconfigured time period (10 minutes typical) should be skipped. When theCPE acquires successfully the new downstream channel, it should transmita DCC-RSP message and wait for a DCC-ACK message from the BS (step 460).If a DCC-ACK is not received by the CPE within configure timeout (2seconds typical) it should retransmit DCC-RSP. These retransmissionsshould be repeated after each period of this timeout until a DCC-ACK isreceived or a configured timeout (typically 30 seconds) has passed sincethe first DCC-RSP transmission. After that timeout the CPE shouldinitiate an initial upstream channel acquisition with initial rangingand registration.

[0097] If the CPE cannot acquire a downstream channel after scanning allthe channels (no “unknown” status channel), it should retry, by priorityorder, the previously failed channels (“One failure” status) (step 440).If the CPE still cannot acquire a downstream channel, it should selectthe channel with success indicator and best MPEG frame error rate (step450). If all the channels are marked as “Two failures”, the entirechannels table should be initialized to “unknown” state and the CPEshould restart initial acquisition starting from the highest prioritychannel, without skipping any previously tried channels (step 470).

[0098] Acquisition of an Upstream Channel

[0099] BS IDU Requirements

[0100] The BS IDU should periodically transmit an Upstream ChannelDescriptor (UCD) message. This message is based on the UCD message thatis defined DOCSIS, with extensions defined above. The UCD message, foreach upstream channel, may be transmitted on all or some of thedownstream channels. Transmitting UCD messages on a subset of thedownstream channels may be used to limit the upstream channel selection,based on the downstream channel selection.

[0101] CPE IDU Requirements

[0102] Initial Connection

[0103] After acquiring a downstream channel, a CPE should acquire anupstream channel. The acquisition process is defined in DOCSIS, with thefollowing changes:

[0104] The CPE should receive UCD messages for all the availableupstream channels (see FIG. 5, step 500). This can be determined by the“number of channels” parameter in the UCD message.

[0105] The CPE should try the upstream channels according to thepriorities for a new CPE (steps 510/520).

[0106] If the CPE has finished successfully ranging on an upstreamchannel, it should continue to test all the others upstream channels, ifany, with the same priority (step 530). The one of these equal prioritychannels that requires the minimal transmitting power is selected (step540).

[0107] The specific method of priorities allocation is depending on aspecific vendor implementation. It is expected that channels that ableto provide better service, based on modulation, symbol rate and currentload will have higher priority. This way a CPE IDU will use the bestchannel it can use, choosing from channels with possibly differentsectors, frequencies, and modulation scheme and symbol rate. Consideringthe current channels load when allocating priorities enables the BS IDUto balance the load between the channels.

[0108] Changing of an Upstream Channel

[0109] Changing of an upstream channel may be desired for improvement ofinitial selection, load balancing, because of system and channelschanges.

[0110] It is expected that the BS should initiate such changes, usingthe DOCSIS UCC-REQ and UCC-RSP messages. Algorithms that use thesefeatures are left for BS vendor specific implementations.

[0111] While the embodiments, applications and advantages of the presentinvention have been depicted and described, there are many moreembodiments, applications and advantages possible without deviating fromthe spirit of the inventive concepts described and depicted herein.

[0112] The present invention may be conveniently implemented using aconventional general purpose or a specialized digital computer ormicroprocessor programmed according to the teachings of the presentdisclosure, as will be apparent to those skilled in the computer art.

[0113] Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as will beapparent to those skilled in the software art. The invention may also beimplemented by the preparation of application specific integratedcircuits or by interconnecting an appropriate network of conventionalcomponent circuits, as will be readily apparent to those skilled in theart.

[0114] The present invention includes a computer program product whichis a storage medium (media) having instructions stored thereon/in whichcan be used to control, or cause, a computer to perform any of theprocesses of the present invention. The storage medium can include, butis not limited to, any type of disk including floppy disks, mini disks(MD's), optical discs, DVD, CD-ROMS, micro-drive, and magneto-opticaldisks, ROMs, RAMS, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices(including flash cards), magnetic or optical cards, nanosystems(including molecular memory ICs), RAID devices, remote datastorage/archive/warehousing, or any type of media or device suitable forstoring instructions and/or data.

[0115] Stored on any one of the computer readable medium (media), thepresent invention includes software for controlling both the hardware ofthe general purpose/specialized computer or microprocessor, and forenabling the computer or microprocessor to interact with a human user orother mechanism utilizing the results of the present invention. Suchsoftware may include, but is not limited to, device drivers, operatingsystems, and user applications. Ultimately, such computer readable mediafurther includes software for performing the present invention, asdescribed above.

[0116] Included in the programming (software) of the general/specializedcomputer or microprocessor are software modules for implementing theteachings of the present invention, including, but not limited to,preparing messages, scanning and acquisition of predefined channels,reading designation messages, interpreting channel priorities, changingchannels, and the display, storage, or communication of resultsaccording to the processes of the present invention.

[0117] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed and desired to be secured by letters patent of theUnited States is:
 1. A method for selecting a channel for communicationbetween two wireless devices, comprising: synchronizing a wireless modemwith a wireless hub on a downstream channel of a plurality of downstreamchannels by synchronizing the symbol timing, forward error correctionframing, and recognition of a synchronization message at the wirelessmodem, the channel of the plurality of downstream channels beingtransmitted from the wireless hub to a plurality of wireless modemsincluding the wireless modem; receiving at the wireless modem on thedownstream channel a message comprising information regarding theparameters for communicating over each of the plurality of downstreamchannels; determining a selected downstream channel of the plurality ofdownstream channels for communication with the wireless hub; andresynchronizing the wireless modem with the wireless hub on the selecteddownstream channel of the plurality of downstream channels.
 2. Themethod of claim 1, further comprising: receiving at the wireless modemon the selected downstream channel a message comprising informationregarding priority levels for each of a plurality of upstream channelsassociated with the selected downstream channel; determining a selectedupstream channel of the plurality of upstream channels for communicationwith the wireless hub based upon the priority levels for each theplurality of upstream channels; and resynchronizing the wireless modemwith the wireless hub on the selected upstream channel of the pluralityof downstream channels.
 3. The method of claim 2 wherein the messagecomprising information regarding parameters comprises an instructionthat instructs the first wireless device to synchronize on the selectedupstream channel.
 4. The method of claim 1 wherein the messagecomprising information regarding the parameters for communicating overeach of the plurality of downstream channels comprises priority levelinformation for each of the plurality of upstream channel, the step ofdetermining a selected downstream channel of the plurality of downstreamchannels for communication with the wireless hub comprising selectingthe selected channel based upon the priority level information.
 5. Themethod of claim 1 further comprising a step of receiving at the wirelessmodem on the downstream channel another message comprising informationregarding parameters for communicating over each of a plurality of otherdownstream channels, wherein the step of determining a selecteddownstream channel comprises selecting the selected downstream channelfrom the plurality of downstream channels and the plurality of otherdownstream channels, and wherein the plurality of downstream channelsand the plurality of other downstream channels correspond to differentsectors of the wireless hub.
 6. A method for selecting a channel forcommunication between two wireless devices, comprising: receiving at awireless modem on a downstream channel a message comprising informationregarding the parameters for communicating over each of a plurality ofupstream channels, the wireless modem already being synchronized withthe downstream channel; determining a selected upstream channel of theplurality of upstream channels for communication with the wireless hub;and communicating from the wireless modem to the wireless hub on theselected upstream channel of the plurality of upstream channels.
 7. Themethod of claim 6 wherein the message comprising information regardingparameters comprises an instruction that instructs the wireless modem tocommunicate on the selected upstream channel.
 8. A method forcommunicating between two wireless devices in a communication system,comprising: receiving at a first wireless device on a downstream channela message comprising information regarding parameters for communicatingover each of a plurality of downstream channels, the first wirelessdevice already being synchronized with the downstream channel;synchronizing the first wireless device on a selected downstream channelof the plurality of downstream channels for receiving communication fromthe second wireless device; and receiving communication from the secondwireless device to the first wireless device on the selected upstreamchannel of the plurality of upstream channels.
 9. The method of claim 8wherein the message comprising information regarding parameterscomprises an instruction that instructs the first wireless device tosynchronize on the selected downstream channel.
 10. The method of claim8 further comprising a step of selecting, at the first wireless device,to synchronize on the selected downstream channel based upon priorityinformation for communicating over each of a plurality of downstreamchannels.
 11. The method of claim 8 wherein the downstream channel is acontrol channel not being one of the plurality of downstream channels.12. The method of claim 8 wherein the downstream channel is one of theplurality of downstream channels and the first wireless devicecommunicating with the downstream channel immediately afterinitialization.
 13. The method of claim 12 wherein the downstreamchannel has a lowest information rate of the plurality of downstreamchannels.
 14. The method of claim 8, further comprising: receiving atthe first wireless device on the selected downstream channel a messagecomprising information regarding priority levels for each of a pluralityof upstream channels associated with the first wireless device;determining a selected upstream channel of the plurality of upstreamchannels for communication with the second wireless device based uponthe priority levels for each the plurality of upstream channels; andre-synchronizing the wireless modem with the wireless hub on theselected upstream channel of the plurality of downstream channels. 15.The method of claim 14 wherein the message comprising informationregarding priority levels for each of the upstream channels comprises aninstruction that instructs the first wireless device to synchronize onthe selected upstream channel.
 16. The method of claim 8 furthercomprising a step of receiving at the first wireless device on thedownstream channel another message comprising information regardingparameters for communicating over each of a plurality of otherdownstream channels, wherein the step of synchronizing the firstwireless device on a selected downstream channel comprises selecting theselected downstream channel from the plurality of downstream channelsand the plurality of other downstream channels, and wherein theplurality of downstream channels and the plurality of other downstreamchannels correspond to different sectors of the second wireless device.17. A wireless communication system, comprising: a wireless hubconfigured to send downstream communications on at least one of a set ofpredefined downstream channels and receive upstream communications on atleast one of a set of predefined upstream channels; at least onewireless modem configured to receive said downstream communications, andsend said upstream communications; wherein said wireless modemcomprises, an acquisition unit configured to acquire a predefineddownstream channel transmitted by said hub and read DCD messagesdescribing available downstream channels, a scanning unit configured toscan the available downstream channels, and a selection unit configuredto select the best available downstream channel.
 18. The systemaccording to claim 17, wherein said wireless modem further comprises achannel quality unit configured to build a list of available channelsindicating a quality of reception on each channel.
 19. The systemaccording to claim 17, further comprising: a channel change unit having,a frame error rate indicator configured to identify when a frame errorrate of a current downstream channel is unacceptable, and a re-lockingmechanism configured to acquire a new downstream channel.
 20. The systemaccording to claim 19, wherein: said re-locking mechanism performs are-locking method, comprising the steps of, scanning downstream channelstransmitted DCD messages from said hub in an order based on priority andattempting to lock onto the channels scanned; re-scanning each of saiddownstream channels if none was locked onto; selecting a channel basedon an alternate criteria if none of said scanning and re-scanning stepsresulted in a channel lock, and attempting to lock onto the selectedchannel; and re-initializing all channel information and re-startingchannel acquisition if said selecting step did not result in a channellock.
 21. The system according to claim 20, wherein said alternatecriteria is an MPEG frame error rate.
 22. A communication device,comprising: a hub configured to send downstream communications on atleast one of a set of predefined downstream channels and receiveupstream communications on at least one of a set of predefined upstreamchannels; wherein: said hub includes a DCD message generator thatconstructs at least one DCD message sent on said downstream channels;and said at least one DCD message defines all downstream channelsutilized by said hub.
 23. A modem unit for use in a communicationsystem, comprising: a reception unit configured to receive downstreamcommunications on a current downstream channel; and a downstream channelselection unit to read DCD messages received by said reception unit andselect a best available channel as said current downstream channel frompriorities contained in said DCD messages.
 24. The modem unit accordingto claim 23, further comprising: a transmission unit configured totransmit data from said device on a current upstream channel; and anupstream channel selection unit configured to select the currentupstream channel based on priorities of upstream channels described inan UCD message received by said reception unit.
 25. The modem unitaccording to claim 24, wherein said upstream channel selection unit andsaid downstream channel selection unit include a change channelmechanism configured to change either the current upstream channel orcurrent downstream channel based on the priorities contained in therespective DCD and UCD messages.
 26. The modem unit according to claim25, wherein said upstream channel selection unit and said downstreamchannel selection unit use different priorities for selecting channelsfor initial communications and for changing a current upstream ordownstream channel.
 27. The modem unit according to claim 23, whereinsaid modem is pre-configured to use a particular cell or sector of awireless hub to acquire and receive said downstream communications. 28.The modem according to claim 24, wherein said downstream channelselection unit selects the current downstream channel of a sector basedon a highest amount of power of available channels, and said upstreamchannel selector selects the current upstream channel based on a samesector of the selected downstream channel.